Large Home Systems

Mar 12

High-performance Residential Off-Grid Systems

Off-grid solar systems used to power larger homes, workshops, and commercial properties are very different from small-scale systems. These systems should be carefully designed by an experienced professional to ensure long-term performance, reliability, and safety. A poor design or underestimation of loads can result in system failure, shortened battery life, and significant additional costs.

If you're powering a large home, homestead, or rural business, you need a robust, reliable, and scalable solution that delivers power day and night, through all seasons, and keeps up with high-demand appliances, even across multiple buildings or micro-grids.

Who Are These Systems For?

Large homes or homesteads
Rural properties with large single-phase loads
Homes with electric cooking, water pumping, multiple fridges/freezers
Properties running high-surge appliances like air-conditioning, compressors or power tools
Those seeking a reliable, scalable 3-phase off-grid solution.

🌾 Off-Grid System Costs for Large Homes and Farms

Powering large homes, multi-building properties or rural farms requires a more robust system design — often with 20 kW or more of solar, 35 to 60 kWh+ of usable battery storage, and a 10 to 15 kW single-phase inverter (or a 20 kW+ 3-phase inverter system).

These high-capacity systems typically cost between $40,000 and $90,000+, depending on site-specific needs and installation complexity. 3-Phase inverter systems are generally 25% more expensive to install. Properties with high pumping, refrigeration, or workshop loads may require additional solar and storage capacity, especially during extended periods of cloudy weather. While more expensive upfront, these systems are engineered for reliability, autonomy, and future scalability.

Victron 3-phase off-grid power system - Installed at the Kinglake Whiskey Distillery

System Sizing Considerations

The most important factor in designing a larger off-grid system is understanding the daily energy usage (measured in kilowatt-hours, or kWh), with a focus on winter heating loads. For all-electric off-grid homes, the daily energy consumption can range from 20 to 30 kWh per day or higher, depending on the household's efficiency and the number of appliances installed.

🔌 Daily Energy Needs

Typical daily energy usage: 15 to 30+ kWh per day

May include multiple high-surge devices (e.g. pumps, welders, motors)

Example Load Table - Large Off-Grid Property

  
    


  
      Appliance
      Power Rating (W)
      Daily Use
      Energy Use (Wh)
    

  
      LED Lights (x10) (whole house)
      10 W
      6 hrs/day
      600 Wh
    

      Refrigerator
      120 W
      24 hrs (cycled)
      1100 Wh
    

      Chest Freezer
      100 W
      24 hrs (cycled)
      1000 Wh
    

      Washing Machine
      500 W
      1 hr/day
      500 Wh
    

      Dishwasher
      1200 W
      1 cycle
      1.2 kWh
    

      Electric Oven
      2500 W
      1 hr/day
      2.5 kWh
    

      Split-system A/C
      1500 W
      6 hrs/day
      9.0 kWh
    

      Bore / Pressure Pump
      800 W
      1.5 hrs/day
      1.2 kWh
    

      Wi-Fi, Laptops, TVs
      200 W
      6 hrs/day
      1.2 kWh
    

      Workshop Loads (tools, etc)
      2000 W
      1 hrs/day (avg)
      2.0 kWh
    

      Total Estimated Daily Usage
      —
      —
      22 kWh/day
    


  

Notes:

Larger systems in this category may include additional kitchen appliances, such as induction cooktops, or multiple split systems used for extended periods, resulting in usage above 25 kWh/day.
Seasonal changes, building efficiency, and battery losses (approx. 8–12%) will be factored into the final system design.

Try our free off-grid calculator

☀️ Solar Array Sizing

In systems of this scale, oversizing the solar array is highly recommended to ensure adequate battery charging and load coverage, even on winter days and during periods of cloudiness.

Typical system specs:

10 kW to 18+ kW solar PV array
Multiple MPPT strings on different roof sections (often split east/north/west or roof + ground-mount)
High-efficiency N-type solar panels with excellent winter performance

Many clients opt for a 15–20 kW+ solar array to boost energy autonomy throughout winter and minimise generator runtime.

⚡ Inverter System & Load Management

Larger systems require powerful inverters to handle high continuous loads and simultaneous appliances across multiple circuits.

Recommended inverters and sizes: 7.5 kW to 15 kW for single-phase homes

Selectronic SP PRO — Australian-made, high surge rating and capability
Victron MultiPlus-II or Quattro — modular, flexible, cost-effective option
Deye all-in-one inverter options for compact, cost-effective installations

3-phase systems may be required for:

Large pumps
Industrial tools or processing equipment

We can also incorporate load prioritisation and smart shedding to protect batteries and keep essential systems running during peak loads or battery lows.

🔋 Battery Storage Capacity

Battery banks in this category need to deliver multiple days of autonomy for large energy users.

Typical battery sizing:

25 to 60 kWh usable storage
Modular lithium (LFP) rack-mount systems using brands like:
- PowerPlus Energy (Australian-made, rack-based)
- Discover AES (Smart, Rack-mount)
- Pylontech outdoor-rated IP enclosures
- AERL (Australian, Smart, Rack-mount)
Expandable architecture — batteries can be added later as loads grow

We also install outdoor-rated enclosures or battery rooms to meet safety regulations and comply with AS/NZS standards.

🔄 Generator Integration

All large-scale off-grid systems should incorporate a backup generator. In high-demand scenarios or winter conditions, a well-matched generator ensures energy security and efficient battery charging.

Key features:

Auto-start generators controlled by the inverter
Intelligent control settings to only run at specific times or when the load exceeds threshold levels.
Generator oversizing for bulk charging or load-pass-through

We can integrate auto-start diesel or petrol generators of any brand, including Kubota, Yamaha, and Honda, with optional manual bypass and silent running features.

Custom Design and Fully Compliant

At Transfer Solar, we specialise in designing and building advanced off-grid and hybrid systems for large homes and small commercial operations. With over 14 years of experience, we’ve helped farms, camps, and rural businesses throughout Victoria become energy-independent with professionally engineered power systems that perform in even the harshest conditions.

Unlike fixed solar kits or generic cabinets, Transfer Solar designs and builds every system to your exact requirements, including:

Indoor or outdoor battery options
Weather-rated pre-wired switchboards
Generator and auto-start compatibility
Allowance for future expansion (solar, battery, inverters)
Full SAA certification and compliance with AS/NZS standards
Pre-programmed and ready for fast installation
Installation by our experienced off-grid electricians

We also design for:

High-load diversity (sheds, water pumping, electric cooking)
3-phase distribution
Load monitoring and remote access (Victron VRM, Select.live)

Why Choose Transfer Solar?

As a qualified engineer and SAA-accredited off-grid specialist, I’ve personally designed and commissioned dozens of advanced off-grid systems across Victoria — from eco-lodges to intensive commercial operations. I understand not just how to size a system, but how to make it reliable, flexible, and compliant with current regulations and rebate frameworks.

Every system is:

Designed specifically for your load profile
Built with premium components
Tested and delivered ready to run
Supported by experts with over a decade of real-world off-grid experience

✅ Start Planning Your System

👉 Contact Transfer Solar to discuss your ideal off-grid or battery system.

Jason Svarc